Title : Non-Coplanar Volumetric Modulated Arc Therapy for Brain Tumours Using an O-Ring Gantry Linear Accelerator: A Dosimetric Evaluation

Purpose: This study evaluates the dosimetric advantages of Non-Coplanar Volumetric Modulated Arc Therapy (ncVMAT) over Coplanar Volumetric Modulated Arc Therapy (cVMAT) enabled by a novel O-ring gantry that permits couch rotation for Brain Tumours.

Methods: Fifteen patients with primary or metastatic brain tumors were retrospectively replanned using coplanar and non-coplanar VMAT techniques. All plans were generated for delivery on an Panacea Siddarth-II superia O-ring gantry linear accelerator. Dosimetric parameters including PTV coverage, conformity index (CI), homogeneity index (HI), gradient index (GI), doses to organs at risk (OARs), low-dose spillage, and normal brain integral dose were compared.

Results: Both techniques achieved equivalent target coverage. NC-VMAT significantly improved conformity and gradient indices while reducing maximum dose to the brainstem and optic apparatus. Normal brain V12Gy and V5Gy were reduced with NC-VMAT. Integral dose to uninvolved brain tissue was lower in the non-coplanar technique. Treatment time increased modestly due to couch rotation.

Conclusion: Non-coplanar VMAT delivered on an O-ring gantry linear accelerator is feasible and provides superior dose conformity and OAR sparing in selected brain tumor cases.

Dr. K R Muralidhar studied Radiological Physics at the Bhabha Atomic Reserch Center, India in 1996 and post graduated in MSc Tech in 1995. He then joined the Manipal Hospitals as Medical Physicist. He received his PhD degree in 2008. He worked in various institute like Indo-American Cancer Hospital and American Oncology Institute as Chief Medical Physicist. Now he is working as Director of Physics in Karkinos Healthcare . He also completed Master of Health Administration and Independent Director from Indian Institute of corporate affairs. He has more than 90 publications and presentations including IAEA, AAPM etc.